1) Field of the Invention
The present invention relates to a motor having a dynamic pressure bearing apparatus and a manufacturing method thereof, and more particularly to a motor including a dynamic pressure bearing apparatus rotatably supporting a rotor shaft member with respect to a fixed bearing member.
2) Related Art
In recent years, a motor with a dynamic pressure bearing apparatus which rotatably supports a rotating shaft has been used to rotate components such as magnetic disks, polygon mirrors or optical disks at high speeds. Motors having a dynamic pressure bearing apparatus as shown in FIG. 4, for example, include a rotating shaft member 2 rotatably inserted into a bearing sleeve 3 as a fixed bearing member. The rotating shaft member 2 is mounted in a rotating hub 1 to carry a recording disc.
A radial dynamic pressure bearing RB is formed of a dynamic pressure face provided on the outer circumferential face of the rotating shaft member 2 and a dynamic pressure face provided on the internal circumferential face of the bearing sleeve 3. These two faces are disposed with a narrow gap radially and a lubricating fluid such as air or oil is contained in the gap.
A thrust plate 4 is fixed to the rotating shaft member 2 and two dynamic pressure faces provided by the thrust plate 4 and a dynamic pressure face of the bearing sleeve 3 and a counter plate 5 are disposed to be faced in proximity in an axial direction with a predetermined narrow gap. A lubricating fluid such as air or oil is injected into the narrow gap of a thrust dynamic pressure bearing SB.
The lubricating fluid is pressurized by a pumping operation of a fluid compression means (not shown), that is, dynamic pressure generating grooves provided on at least one of the dynamic pressure faces in the radial dynamic pressure bearing RB and the thrust dynamic pressure bearing SB. Thus, the rotor shaft member 2 is rotated in a floated condition in a radial direction and in a thrust direction respectively by means of the resultant dynamic pressure.
A motor having the dynamic pressure bearing apparatus is assembled using the following steps. A rotor hub 1 is first fixed to a rotating shaft member 2 and the rotating shaft member 2 is inserted inside a bearing sleeve 3. A thrust plate 4 is then accommodated in an end portion of the rotating shaft member 2. A counter plate 5 is then mounted to an aperture portion of the bearing sleeve 3 providing the thrust plate 4 between the counter plate 5 and the bearing sleeve 3. A radial clearance between the counter plate 5 and the bearing sleeve 3 is then sealed by adhesive material 6
When oil is used as the lubricating fluid, deaeration in the radial dynamic pressure bearing RB and the thrust dynamic pressure bearing SB of the bearing assembly occurs. The oil is filled inside each of the bearing sections by the vacuum attraction force generated at the time of deaeration. After removing excess oil which stuck to the bearing assembly, a ring-shaped rotor magnet 7 is fixed to the internal circumferencial face of the rotor hub 1 by an adhesive material, intervened with a back yoke plate between them.
Alternatively, in the case where a motor frame 11 on which a flexible circuit board is installed and intervened with an insulating paper, a stator core 13 with a stator coil 12 wound thereon is fitted and fixed to a core holder 14 with encapsulated electrical wiring. In the internal circumference of the core holder 14 of the stator assembly, the bearing sleeve 3 of the rotor assembly is inserted and fixed by adhesion.
In this case, when assembling the stator and the rotor, the appropriate positional relationship between the stator assembly and the rotor assembly is attained with a jig. Using the jig, the stator assembly and the rotor assembly are assembled such that a predetermined positional relationship is maintained between the assemblies.
Establishing the proper positional relationship between the stator assembly and the rotor assembly using the jig is very difficult and time consuming. In particular, when a motor accommodates a media disc, it is necessary to adjust the height parallelism of the disc placing face of the rotor assembly with a high degree of accuracy with respect to the reference plane of the stator assembly. In addition, be allocated for the adhesive material used to solidify.
Therefore, many hours are required to adjust the jig. This causes a reduction in productivity. Furthermore, many highly precise jigs must be prepared, which leads to the problem of increased cost for the manufacturing facility. Therefore it is desirable to provide a motor including a dynamic pressure bearing apparatus, that can be assembled with a stator assembly and a rotor assembly with a level of ease and with a high degree of accuracy.
A motor having a dynamic pressure bearing apparatus includes a fixed bearing member mounted to a motor frame, a rotating shaft member rotatably inserted with respect to the fixed bearing member and a lubricating fluid injected into a gap portion between the fixed bearing member and the rotating shaft member. The rotating shaft member is supported by a dynamic-pressure caused by the lubricating fluid. In addition, the motor frame is provided with a generally cylindrical bearing hold member that holds and fixes a bearing member. The bearing hold member includes a bearing contacting portion which abuts against the fixed bearing member or one part of the assembly including the fixed bearing member in an axial direction for positioning the fixed bearing member in a normal position in an axial direction.
Other features and advantages of the invention will be apparent from the following detailed description, taken in conjunction with the accompanying drawings that illustrate, by way of example, various features of embodiments of the invention.